1. Field of the Invention
This invention relates to a coupling mechanism, and in particular to a self-locking bayonet-type coupling mechanism of the type in which, following initial axial insertion of one coupler half in the other coupler half, a locking sleeve is automatically rotated into a locking position to prevent unintended decoupling due to shocks or vibrations. Unlike prior coupling mechanisms of this type, the invention further adds an axial coupling force which draws the coupler halves together during rotation of the locking sleeve into the locking position, and which is maintained continually following completion of coupling.
The coupler of the invention may be used in electrical, hydraulic, or pneumatic coupler systems, and is especially advantageous in coupler systems requiring sealing because it applies a continuous axial force to the interface between mated couplers.
2. Description of Related Art
Automatically locking couplers, in which a locking sleeve is rotated against a spring force during initial insertion of one coupler half into the other, and permitted to rotate back into a locking position upon completion of insertion, are known from U.S. Pat. Nos. 5,067,909 and 5,167,522.
These patents disclose a coupling mechanism, when one coupler half is inserted into the other half, a sleeve on one half is caused to rotate against a torsional spring force as a result of the camming action of complementary triangularly-shaped tabs on the sleeve and the inserted coupler half, the restoring force of the spring causes the sleeve to rotate into the locking position after the complementary tabs have passed each other so that the tabs prevent disengagement of the coupler halves until the sleeve is twisted to permit the tabs to clear each other during uncoupling.
A similar coupler is disclosed in U.S. Pat. No. 5,662,488 and illustrated in FIGS. 1-3 herein. In this coupler, L-shaped slots 1 in one coupler half 2 and bayonet pins 3 on a coupling sleeve 4 are used to rotate the coupling sleeve relative to the other coupler half 5, so that when the coupler half to which the sleeve is mounted is inserted axially into the other coupler half, a torsional restoring force forces the bayonet pin into the base of the L-shaped slot. Instead of utilizing a torsion spring, the torsional restoring force is provided by a second set of cam surfaces 6 on the inserted coupler half, which are arranged to cam a corresponding second set of pins 7 on resilient portions 8 of the sleeve in a radially outward direction, the torsional component of the restoring force on the second set of pins caused by the second set of cam surfaces causing the sleeve to rotate to the latching position when the first bayonet pin reaches the base of the L.
Inherent in both of these self-locking designs is the problem that a certain amount of play is necessary to permit the complementary locking structures, i.e., the triangular tabs of U.S. Pat. Nos. 5,067,909 and 5,167,522, and the bayonet pin and slot of U.S. Pat. No. 5,662,488, to clear each other so as to permit rotation into the locking position in response to the torsional force, and also as a result of manufacturing tolerances. The presence of play between the mating coupler halves increases wear on contacting parts, and in case of a sealed coupler, can compromise the seals at the interface between the mating halves of the coupler, causing the seals to acquire an elastic set due to failure of the coupler halves to bottom out or stay in the desired mating position.
On the other hand, it is known in the context of conventional, non-self locking coupling arrangements, to solve the problem of tolerances or play between mating connector halves by applying an axial force on the mating coupler halves. Examples of designs that apply a pre-load or axial force to the coupling include U.S. Pat. Nos. 3,805,379 and 4,820,185. In the design disclosed in U.S. Pat. No. 3,805,379, which is illustrated in FIG. 4 herein, the axial force results from rotating a bayonet coupling sleeve so that a bayonet pin traverses the corresponding groove past the point at which contact between the coupler halves is established and on to the end of the groove, against a purely axial pre-load provided by a spring arrangement. The component of the extended travel distance in the direction of mating defines the pre-load on the coupler halves.
Because the pre-load of the illustrated conventional bayonet coupler is applied at the end of travel of the bayonet in the corresponding groove, completion of coupling requires an increase in the manually applied rotational force, starting at the point of contact, at which point the pre-load spring starts to compress. As a result, this arrangement is unsuitable for use in an automatic locking mechanism of the type disclosed in U.S. Pat. Nos. 5,067,909, 5,167,522, and 5,662,488, in which the force applying springs are compressed during initial insertion. In addition, the conventional axial pre-load arrangement is unable to accommodate manufacturing tolerances that might affect the actual pre-load.
The present invention, on the other hand, combines the axial pre-load of U.S. Pat. No. 3,805,379 and the self-latching arrangements of U.S. Pat. Nos. 5,067,909, 5,167,522, and 5,662,488, by using a modified torsional force generating arrangement rather than the purely axial force of the mechanism illustrated in U.S. Pat. No. 3,805,379, to generate both the rotational and axial forces, and thereby provide a coupler that eliminates the disadvantages of both prior types of coupler. In the present invention, not only is a torsional force applied to the latching sleeve to cause it to move into a latching position, but a transverse component of the torsional force is also utilized to draw the halves of the coupler together while at the same time rotating the sleeve into the latching position.
No other prior coupling mechanism offers the combination, provided by the invention, of a coupler in which the halves of the coupler are both drawn together and locked so that the coupler halves can be mated using a purely linear motion with a minimum of effort, movement of the couplers into the final mated position being accomplished automatically without the need for human intervention or the possibility of incompletely mating due to lack of feedback.